The flap over Ann Coulter’s tweet — calling the president a “retard” — is a sideshow. Coulter’s a symptom, not the disease.

During Monday’s presidential debate, Coulter sent this to her 263,000 Twitter followers: “I highly approve of Romney’s decision to be kind and gentle to the retard.” Her insult, as usual, was aimed at President Obama.

Coulter’s cheap shot boomeranged: The conservative columnist was roundly criticized — even by those she typically supports — for her crass insensitivity.

The most elegant came from John Franklin Stephens, a Special Olympics athlete who penned an open letter to Coulter. In it, he said mocking people we dislike often inflicts collateral damage.

“You assumed that people would understand and accept that being linked to someone like me is an insult,” Stephens wrote. “You, and society, need to learn that being compared to people like me should be considered a badge of honor.” Was he writing to Coulter, or all of us?

The R-word is uttered too often, by too many. It’s a degrading put-down, reinforcing old, hurtful stereotypes about people with disabilities.

Coulter isn’t the first. In a 2009 “Tonight Show” appearance, Obama himself joked that his bowling skill “was like the Special Olympics or something.” He apologized, but the damage was done.

If Coulter apologizes, presume it will be unconvincing. This wasn’t her first “retard” tweet. She used it to insult Obama supporters in September. Two weeks ago, she tweeted: “Last Thursday was national ‘coming out’ day. This Monday is national ‘disown your son’ day.”

Face it, she’s just mean.

If she has any capacity for good, it’s as a cautionary tale. If we find ourselves saying anything Ann Coulter might say, that’s a warning to choose our words more carefully.